Defense lawyers and relatives of jailed Venezuelan opposition leader Leopoldo Lopez are demanding an appeal to his nearly 14-year sentence this week following revelations by one of his prosecutors that the trial was a sham.

Mr. Lopez, convicted in September for inciting violence in last year’s antigovernment protests, has already spent more than 19 months in prison.

“This was a totally political trial which should be nullified. All of Leopoldo López’s human rights were violated because he was not able to present any witnesses or evidence,” prosecutor Franklin Nieves told The Wall Street Journal this week in his first interview since fleeing to Florida with his family. Mr. Nieves is requesting asylum in the US, the Associated Press reports.

The Nieves disclosure “offered confirmation for what the country’s opposition and international observers believed from the day Mr. López surrendered to police in February of last year,” reports The WSJ. “[T]hat his arrest was a political move by [President Nicolás] Maduro’s government as part of a broad bid to tamp down dissent, just as nationwide anti-government protests were kicking off.”

Nieves’ revelation puts the government in a precarious situation in the leadup to December midterm elections. The election is the first in the 30 months since former President Hugo Chávez died that the ruling party is not doing well in the polls, according to University of Glasgow professor Iñaki Sagarzazu, writing on the Venezuela Politics and Human Rights blog. Nieves’ desertion and apology are likely to fuel Venezuela’s political crisis.

President Maduro’s popularity has plummeted along with oil prices. Venezuela faces widespread oil shortages and one of the highest inflation rates in the world, a result of poor management of the oil-rich economy. The government has engaged in nationalistic strategies to win support in recent months, like closing the border with Colombia and reigniting territorial claims in Guyana. Lopez’s conviction was an effective way for the government to discredit opposition leaders.

Venezuela’s Attorney General Luisa Ortega denied Nieve’s claims that he was pressured to provide false evidence in Lopez’s trial.

"At the state prosecutors' office we don't pressure anyone," Ms. Ortega said in a televised statement, adding that Nieves’ allegations were not grounds to overturn Lopez’s verdict.

On Monday, Nieves posted another video on Venezuelan news site La Patilla outlining how the government had tried to arrest Lopez at a previous antigovernment protest, but had failed. He has promised to continue releasing evidence that Lopez was targeted and steamrolled by the government.

This isn’t the first time a member of the judiciary has spoken out against a Chavista administration, which many critics say controls the justice system and uses it as a tool of intimidation, Reuters reports. A supreme court judge fled the country in 2012, later charging that the government "systematically interven[ed] in the courts for political ends," Reuters reports.

In Nieves' first video, which went online last week, he appealed to other prosecutors and judges in Venezuela to stand up for justice, The New York Times reports. “I invite you to tell the truth as I am doing now. I want to do the right thing, stop being afraid and tell the truth. I want you to be brave, raise your voices.”